I. Field of the Invention.
The present invention relates generally to the field of weapon stocks. More particularly, the present invention relates to single pour, polyurethane stocks suitable for use with rifles and shotguns and single pour, polyurethane pistol hand grips.
II. Description of the Related Art.
Stocks for various weapons have been and continue to be manufactured from wood. Not only does wood provide natural beauty, it also provides workability and relatively light weight. A craftsman can engrave, bore or generally work the wood to add any desired ornamental or functional feature to the stock. However, wood is very sensitive to atmospheric relative humidity, resulting in the wood stock shrinking in "dry" conditions and expanding in "wet" conditions. For competitive marksmen, this is particularly bothersome since relative humidity from one location to another varies. In fact, relative humidity can vary at a single location throughout a given day. As a result, the competitive marksman often needs to recalibrate the weapon's sight at each shooting match to overcome this disadvantage. This recalibration, or zeroing, of the weapon is time consuming. Due to the limited time between the rounds of the match, it may not be possible to recalibrate the weapon and the marksman is therefore hampered.
To alleviate this problem, craftsmen developed synthetic stocks which do not react to the relative humidity. This enables the marksman to travel from one location to another with the weapon zeroed for his or her body. Unfortunately, the physical construction of such synthetic stocks do not allow modifications for ornamental or functional features like wood stocks. Further, because the synthetic materials are generally more dense than wood, it is desirable for the weight of the stocks be reduced to that of comparable wood stocks. Typically, these synthetic stocks have outer skins which may not be ruptured without loss of structural integrity in weapon firing applications.
Popular synthetic stocks are currently commercially available. One such stock manufactured by Bell and Carlson, Inc. has a hollow core with successive layers of graphite, KEVLAR, fiberglass and an outer skin of polyurethane. Another popular stock by McMillan Fiberglass Stocks, Inc. is manufactured by an injection-molding process in combination with an epoxy impregnated, high-pressure laminated fiberglass cloth and chopped glass strands.
A gun stock of expanded cellular plastic material described in U.S. Pat. No. 2,753,642 by Sullivan has a preformed external skin of durable material and a core of low density, rigid and expanded cellular plastic within and secured to the skin. The skin is a thermoplastic sheet of tough, synthetic and rubber-like plastic. Poured into the skin to harden and cure, the core is a reactant alkyd resin meta-toluene-diisocyanate mixture or a phenolic type foam/cellular plastic. Although the core appears to be poured, the stock is made of two parts and the strength is derived from the skin. Even though Sullivan mentions polyurethane as a suitable material, the problems of the stock weight and the manufacture of a solid, single pour stock are not addressed.
U.S. Pat. No. 3,299,558 issued to Karl describes a metal gun barrel with encircling plastic layer and integral plastic sight. A molded gun stock is provided which is an integral part of the plastic coating. Suitable plastics are described as nylon, TEFLON, neoprene, polyvinyl, polyethylene, polyurethane and acetal resin. The process by which the stock is molded is not described within the patent.
A polyurethane foam gun stock is described in German Patent Number 2017087 by Allgaier. This stock has a hard, smooth and non-porous skin and a core having a density which is 50% of the skin density. The skin is described as being more dense than wood and the core is describe as being less dense than wood. It is clear that the strength of the stock is derived from the skin and the stock is not manufactured by a single pour process.